Support external editors with no ODB support for different file types

Description

Maybe you could add the option to include external editors (user-defined) for different file types (specially images: gif, png, jpg, tif, psd...).

I think you support (text editors) which observe a special "protocol" to communicate with external apps. Can't you "monitorize" the downloaded file for changes, so when the user edits the file and click "Save", you start the uploading process?